[New Feature]: Add parametrization for python binary called

[sval-dev]

Checked for duplicates

Yes - I've already checked

Alternatives considered

Yes - and alternatives don't suffice

Related problems

The Measure tool internally calls private/api/2ptsToProfile.py, to generate a profile, and if "python" is not present in the path, or does not point to a version with the needed dependencies installed (e.g. GDAL), the profile does not show up.

Describe the feature request

On some systems, python might not be present (e.g. only python or python3.6 might be present), or the default python might not point to an environment that has the required dependencies installed (e.g. when the deps are installed into a venv or conda env).

Given that, it might be useful to parametrize the path to the python binary used by scripts/server.js in several locations, the first of which is on Line 654
One potential implementation would be to add a new env variable (e.g. PYTHON_EXE) for the python executable which defaults to "python", so behavior remains unchanged if it is not set.

The workaround for users in the meantime is to modify their PATH such that there is a "python" executable present, and that the first such executable found points to the python executable within the environment they want.